This invention relates to integrated circuit devices. More particularly, this invention relates to a flexible circuit connector for a stacked integrated circuit module.
Designers of computers and other electronic systems constantly strive to miniaturize integrated circuit (xe2x80x9cICxe2x80x9d) devices and modules to place more circuits in smaller spaces while operating at higher speeds. Because of this demand, there is a need to develop smaller, yet denser, memory packages, or modules, and other small, yet dense, modules containing integrated circuit devices, such as microprocessors, memory devices, DMA devices, etc. Typically, these modules not only require external electrical connections to other modules or external electronic circuits, but also, they require internal communication paths, or buses, for data communication between the discrete semiconductor devices within the module itself. The problem then has arisen with regard to how to create electronic pathways, or buses, for stacked packaged integrated circuits that are physically external to the integrated circuit package and provide an external communication path from the circuit board to each of the individual integrated circuit devices within the stacked module.
Various schemes have been developed to provide these interconnections. Rail bus systems, for example, are described in U.S. Pat. Nos. 5,279,029 and 5,484,959, both of which are commonly owned by the assignee of the present invention. These systems use external bus rails to interconnect the external leads of the stacked IC devices. Unfortunately, rail systems can be costly. Rail-less schemes have been developed that use various means for interconnecting the external leads from the stacked devices. For example, U.S. Pat. No. 4,696,525 to Coller et al. teaches a socket connector for coupling adjacent devices in a stacked configuration to one another. The socket has external conductors that interconnect leads from like, adjacent devices to one another. Sockets, however, are limited in several respects. They are not versatile in their ability to implement complex interconnections. In addition, such sockets, which have relatively thick, plastic bodies, act as heat insulators between adjoining upper and lower (major) package surfaces, which can inhibit the module""s overall ability to dissipate heat. Co-pending application Ser. No. 08/645,319 to Burns, which is also commonly owned by the assignee of this invention, discloses an external intermediate lead frame for interconnecting adjacent packages. This lead frame solution has improved interconnection and heat transfer capability. However, an even better, more inter-connectively versatile and thermally conductive solution is desired.
Accordingly, what is needed is an improved apparatus for electrically and thermally coupling adjacent integrated circuit devices in a stacked module.
The present invention provides a flexible circuit connector for electrically and thermally coupling adjacent IC packages to one another in a stacked configuration. Each IC package includes: (1) a package having top, bottom, and peripheral sides; (2) external leads that extend out from at least one of the peripheral sides of the package; and (3) an IC inside the package connected to the external leads. In one embodiment, the flexible circuit connector comprises a plurality of discrete conductors that are adapted to be mounted between the upper side of a first package and the lower side of a second package. The flexible circuit connector also includes distal ends that extend from the conductors. The distal ends are adapted to be electrically connected to external leads from the first and second packages to interconnect with one another selected, separate groups of the external leads. In this manner, individual devices within a stack module can be accessed by a circuit card or printed circuit board. This versatility is beneficial in modules such as memory modules, which can have multiple, stacked memory devices.